I got an older 86 Volvo diesel and it smokes a bit(blue crankcases oil). I'm coming up on an emissions inspection test. What would be better to minimize the smoke for the test. Light or heavy grade or natural oil or synthetic?? Any recommended additives?
Unfortunately in your case, the smoke is most likely due to sticking rings... a problem with those loveable ole D24 engines. Heavier weight oil will help I believe, and maybe even some Lucas Motor Oil Stabilizer (Motor Honey), but your best current bet is going to be a product called AutoRX which will help un-stick those rings:
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The best stuff was Lubro-Moly OL Shalaam Spulung, but since it was imported to the USA/Canada as "Engine Flush", the contents have changed significantly and it's not very effective anymore.
If you really want to cure the problem for good, a rebuild is in order. Replace those rings and change your oil ever 3000 miles after your rebuild with quality stuff (or 7500+ with quality synthetics) and you'll be good for several hundred thousand more miles without problem, and much more power/less smoke. Volvo's worst call ever was putting 7000 mile reccomended oil-change intervals in their 1980's volvo diesel owners manuals... it sent most of em to the junkyard at right around 160,000 miles. Anything to make a diesel sale in the 80's, eh?
By the way, a few of us diesel-brickers have a Yahoo! group just for us... come on over and join up!
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If you're an '86, you must have the last year of the 740 Turbodiesel... invest some time and a few dollars on that rebuild, and you can push 270hp out of that little straight-6 while getting 46mpg on the freeway at 75mph - It's been done! There's a lot of potential in that engine...
Since you have a diesel engine, you probably want a diesel rated oil (e.g. API CH-4 or CI-4, although CF is acceptable for older diesel engines that specified CC or CD); typically these come in 15W-40 conventional or 5W-40 synthetic, though some 10W-30 and 5W-30 varieties may be found. No idea what effect that can have on the smoking, though.
So, what's the best oil to keep down emissions(blue smoke) for now to pass a test; 10-40 Penzoil natural or some 10-40 synthetic(which)? And then use one of these additives on top of that?
If it is burning oil and the test is designed to fail an engine that burns excessive oil then your engine will fail. Get it maintained and repaired properly or scrap the heap if this is uneconomic.
If this is the same engine used in the VW LT van range then it is a miracle if it lasts 160,000 miles. It is an absolute pig which breaks camshafts on a regular basis. The indirect injection throws huge amounts of soot into the oil so that a commercial heavy duty diesel oil is essential to handle the shit. Any synthetic is wasted because it will handle no more soot than any other oil with a similar specification. As it happens the relatively new API CH4 mineral oils are just the ticket for up to 7500 highway miles depending on condition of engine.
If your car is burning enough oil to be smoking, I don't think changing the oil will cause it to burn clean enough to pass the emissions test. You need to stop it from burning oil or it's not going to pass.
I believe in some areas that do emissions testing, if your vehicle is producing visible exhaust smoke then they will not even test it, it's an automatic failure.
The smoke is rather marginal now and any small improvement would allow passage. Light duty desiels are exempt in the US from normal emission testing. So the question remains: What would be the lowest smoker 10-40 natural oil or 10-40 synthetic??
You asked "So, what's the best oil to keep down emissions(blue smoke) for now to pass a test; 10-40 Penzoil natural or some 10-40 synthetic(which)? And then use one of these additives on top of that?"
If you do not like the answers, which mainly consist of something similar to 'stop being a cheap lazy **** and get the fecking thing fixed properly', there is certainly no point in asking the question over and over again which is especially hilarious if your reaction is as above.
Both oils will burn equally. Oil is not designed to be burnt. Fuel, petrol diesel and gas is commonly burnt for power in small internal combustion engines. I am surprised you do not appreciate this, preferring instead to insist on a clean burning lubricating oil. In fact API SL, or in your case API CG4 or CH4 are about the cleanest burning oils you can find but this is only in relation to tested emissions and their effect on cats, not from a smoke point of view. All oils will smoke whether mineral or synthetic when burnt. Only the use of a heavy oil like a straight 40 for the duration of the test might improve things. Get it fixed.
I guess I will let the secret out if nobody else will. Common lavender scented bubble bath is just the thing you need. Cheap and available at any corner drug store. Just fill 'er up! Problem solved.
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